Britain's waterways are under threat from an invasion of exotic crabs that scientists want to trap to protect the environment.

The Chinese mitten crab, so named because of the tufts of brown fur that sprout from its claws, established itself in British waters after arriving as larvae in the ballast of merchant ships in the 1970s. For years the population grew slowly, but recently numbers have surged and the crabs have spread rapidly across the country.

The crabs are the size of dinner plates and are indiscriminate feeders, living off dead vegetation, rotting flesh and any live prey they can get their claws on. They burrow in riverbanks, forcing silt into waterways and making the banks prone to collapse.

Matt Bentley and a team of marine scientists at Newcastle University gathered years of authenticated sightings and mapped how the crabs have colonised territory across the country. Between 1976 and 1999, they spread along the coast at an average speed of 48 miles (78km) per year. But between 1997 and 1999, they colonised the coastline at 278 miles each year. "They're in a phase of rapid expansion, and at this rate, it is likely they will reach all of our major estuaries within a few years," said Dr Bentley. "They could cause serious damage to our native fauna as well as the riverbanks."

The crabs are already well established in the Thames and Essex estuaries, the Humber and Tyne and parts of the North Sea and Channel coasts. Scientists fear that by feeding on native species such as the white-clawed crayfish, salmon eggs and fry, mitten crabs will mirror the environmental damage caused by grey squirrels whose introduction lead to a sharp decline in native red squirrels. "We would like to see groups set up to monitor the spread of the crabs and traps laid in rivers so we can keep a track of the numbers and prevent them spreading," said Dr Bentley.

The crab's testicles are considered a delicacy in Chinese and Japanese restaurants, where they are eaten raw.